If you do much winter driving in Oregon, you have probably seen the Oregon Department of Transportation (ODOT) SNOW ZONE signs that tell you the current requirements for chains or traction tires. Do you know what they mean? Here’s a primer.
You must have chains or traction tires in or on your vehicle; they must be the right size for your vehicle and meet ODOT’s chain requirements.
You must use chains if your vehicle is towing or rated more than 10,000 pounds gross vehicle weight (GVW). Chains must also be used on a trailer or vehicle being towed.
You must use chains if your vehicle is rated 10,000 pounds GVW or less and is towing. You must use chains on any single drive axle vehicle rated more than 10,000 pounds GVW whether towing or not. Chains must also be used on the trailer or vehicle being towed.
You must use chains if your vehicle is towing or is rated more than 10,000 pounds GVW. Chains must also be used on a trailer or vehicle being towed. If your vehicle is rated 10,000 pounds GVW or less and is not towing, you must use chains or traction tires.
Drivers who disobey SNOW ZONE signs are subject to a class C traffic infraction.
A four-wheel or all-wheel drive passenger vehicle is exempt from ODOT’s chain requirements if all of the following are true:
- It has an unloaded weight of 6,500 pounds or less.
- It provides power to both the front and rear wheels.
- It is carrying chains.
- It has mud-and-snow, all-weather radial, or traction tires on all of its wheels.
- It is not towing another vehicle.
- It is not being operated in a manner or under conditions that cause the vehicle to lose traction.
Conditional closures. When travel on a state highway becomes especially hazardous, the Oregon Department of Transportation may impose a conditional road closure that applies to certain types of vehicles, or all vehicles, depending upon the conditions. Typically, ODOT or Oregon State Police will be on site to advise drivers about the closure.
So, what are traction tires anyway?
The Oregon Department of Transportation cryptically defines traction tires “as studded tires, retractable studded tires, or other tires that meet the tire industry definition as suitable for use in severe snow conditions.” Here is an explanation:
The tire industry standard for traction tires is the ASTM F1805 snow traction test, which measures tire performance on snow and ice. Tires that pass the test can display a Three-Peak Mountain Snow Flake. The characteristic feature of these tires is a tread design with bigger gaps than those on summer tires; the gaps allow snow to penetrate into the tread, where it compacts and provides resistance against slipping.
Studs are essentially hard steel pins enclosed in a softer base that wears faster than the pin. To be effective, the pin should protrude at least 1 millimeter (0.04 inches) above the surface of the tire. Studded tires are only legal for use in Oregon from Nov. 1 through Mar. 31.
You won’t find any retractable studded tires in Oregon. Nokian Tyres developed “the world's first non-studded winter tire with studs” to celebrate the 80th anniversary of the winter tire – but it’s just a concept now.